runtype is composed of several utility modules:

  1. dispatch - Provides a decorator for fast multi-dispatch at run-time for functions, with sophisticated ambiguity resolution.

  2. dataclass - Improves on Python's existing dataclass, by verifying the type-correctness of its attributes at run-time. Also provides a few useful methods for dataclasses.

  3. isa - Provides alternative functions to isinstance and issubclass, that understand Python's typing module.

Runtype's integration with the typing module allows to use type signatures such as List[int], Optional[str], or Union[int, str, Callable].

Click on each one to learn more.


$ pip install runtype

No dependencies.

Requires Python 3.7 or up (or Python 3.6 with the dataclasses backport)

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Type verification in classes introduces a slight run-time overhead.

Multiple-dispatch caches call-signatures by default (disable at your own risk!), and should add a minimal overhead after the initial resolution. Dispatch is only 5 to 8 times slower than adding two numbers (see: examples/benchmark_dispatch), which is negligable.

Runtype is not recommended for use in functions that are called often in time-critical code (or classes that are created often).


Runtype uses the MIT license.

Similar projects

  • typical - Provides type verification for classes and methods, with a focus on type coercion.